The invention relates to a paste-like damping medium dispersion for damping mechanical and acoustic vibrations
It is known to use as damping medium an aliphatic or aromatic carboxylic acid ester to which ground graphite and at least one wetting agent are added. The pastelike damping medium dispersions according to the aforementioned application have the disadvantage that they swell elastomers, e.g. on the basis of natural caoutchouc.
The U.S. Pat. No. 3,244,626 (Lyons et al) describes a lubricant comprising a mineral oil and 20 to 40% graphite as thickening substance. This lubricant contains no polyglycol ether or polyglycol ester, no viscosity stabilisers and no wetting agents. It is not suitable as a damping medium dispersion because the lubricant becomes liquid at raised temperatures. Furthermore, the known lubricant based on mineral oil attacks elastomers, thus having a destructive effect on the elastomer components of correspondingly constructed dampers.
The U.S. Pat. No. 2,711,394 (Veatch et al) describes a lubricating liquid comprising a mixture of mineral oil, graphite and aluminium silicates as gelling agent. This lubricating liquid has a viscosity of only 350 to 550 modified Furol seconds at 37.8.degree. C. It should be so thin that it can be applied as lubricating liquid to sliding surfaces with a brush. There is thus no viscous paste involved here either. An important difference between this known lubricating liquid and the plastic, highlyviscous paste according to the invention is that the former contains 87.5 to 96% mineral oil, thus being completely unsuitable for dampers with elastomer components, e.g. engine mountings.
The U.S. Pat. No. 3,812,937 (Abbott et al) describes a lubricant which contains petroleum oil and in which up to 20% of a special montmorillonite is dispersed. The composition and the properties of this lubricant are not comparable with the special composition of the highly-viscous dispersion according to the invention. The known lubricant furthermore attacks elastomers, with the result that the elastomer components of the damper are destroyed prematurely.
A damping medium dispersion was thus needed which does not foam under permanent load, shows good thermal conductivity, is self-sealing and does not attack elastomers based on natural caoutchouc or caoutchouc/isoprene. The damping medium should show a constant shock-absorbing and vibration-damping effect both at low and at high temperatures and also under permanent load. It should take up the energy of shock loads imposed by high and also low-frequency vibrations and convert it into heat. The damping medium may not undergo any hardening under sudden shock load because it should also have a noise-damping effect, especially on so-called body noise. It is also desirable for the dispersion to be noise-insulating.
An essential object of the invention is that the elastomer components contained in some dampers, e.g. engine mountings, are not swollen by the damping medium dispersion.